The two males, aged 38 and 16, were spotted by a U.S. Customs and Border Protection helicopter crew late on Wednesday as they walked up Imperial Beach, a few miles south of San Diego, clutching the dive scooters, the Border Patrol said in a news release.

"That area where they were apprehended is very close to the international border," San Diego sector Border Patrol spokesman Michael Jimenez told Reuters.

"These devices can be used to come north along the coastline and steer into shore ... where they can meet someone who will pick them up in a vehicle and further their entrance into the United States," he added.

Jimenez said agents arrested the two men as they tried to hide in the sand, and took them to a local Border Patrol station for processing.

As security has tightened along the California border in recent years, Mexican immigrants and smugglers have increasingly turned to the sea to slip into the United States.

Last year border police seized 110 vessels and arrested 867 people attempting to slip into the San Diego area by sea, up from 33 vessels seized and 230 arrests two years earlier.

Underwater scooters are among some of the more bizarre methods, which have also included using a surfboard to slip a marijuana load into California.

Jimenez said agents did not find any scuba gear when they arrested the two, and said it was unlikely that the men "were traveling beneath the waves."